The present invention relates generally to connectors and more particularly to input-output style connectors, including connectors that are used to connect signal cables, especially high-speed signal cables, to an electronic device, such as a computer.
Many electronic devices, such as computers, include transmission lines to transmit signals from peripheral devices such as a video cameras, compact disc players or the like to the motherboard of the computer. These transmission lines incorporate signal cables that are capable of high-speed data transmissions. In most applications, the signal cable extends from either the peripheral device itself or a connector on the peripheral device to a connector mounted on the motherboard. These connectors are quite small in keeping with the trend toward reduced size of electronic devices. The size of such connectors may typically be about 8 mm by 6 mm, thereby leaving a connector designer only 48 mm.sup.2 of area in which to develop appropriate connector structure and components in order achieve a desired level of performance of the connector.
Signal cable construction may use what are known as one or more twisted pairs of wires that are twisted together along the length of the cable, with each such twisted pair being encircled by an associated grounding shield. These twisted pairs typically receive complimentary signal voltages, i.e., one wire of the pair may see a +1.0 volt signal, while the other wire of the pair may see a -1.0 volt signal. As signal cables are routed within a computer, they may pass by or near electronic devices on the computer motherboard which create their own electric field. These devices have the potential to create electromagnetic interference to transmission lines such as the aforementioned signal cables. However, this twisted pair construction minimizes or diminishes any induced electrical fields and thereby eliminates electromagnetic interference.
In one current application, these signal cables are manufactured in three different speeds for use with peripheral devices and these three speeds are 800, 1600 and 3200 megabits per second. If the speed of the cable is known to the electronic device, the device may switch to various internal circuits to match the transmission speed capability of the cable. It is therefore desirable to incorporate a means to determine the speed of the cable into the connector itself.
In order to maintain electrical performance integrity from the cable to the circuitry of the device, it is further desirable to obtain a substantially constant impedance throughout the transmission line, from circuit to circuit and to avoid large discontinuities in the impedance of the transmission line. It is known that it is difficult to control the impedance of a connector inasmuch as the impedance of a conventional connector typically drops through the connector and across the interface of the two mating connector components. It is therefore desirable to maintain a desired impedance throughout the connector and its connection to the circuit board.
The present invention is therefore directed to a cable connector for providing a connection between high-speed cables and a printed circuit board that provides a reliable connection with a high level of performance.